Organic electroluminescence includes a phosphorescing compound and a fluorescing compound and it is known that a phosphorescing compound exhibits higher external quantum efficiency. It is also known that in order to allow a phosphorescing material to perform efficient emission, providing a functional layer such as a hole transport layer, an emission layer, a hole transport layer or the like results in enhanced external quantum efficiency.
On the other hand, a production method of an organic EL by a wet process is noted in terms of enhanced use efficiency of materials.
However, problems arose with device production by a wet process, such as uneven emission due to coating mottle. It was also proved that devices produced by a wet process resulted in reduced external efficiency, compared to those produced by a process of vapor deposition.
There was described coating a polymeric material with a solvent (such as described in, for example, Patent document 1), however, there was no description with respect to a problem related to unevenness in coating a low molecular material and nothing was reported with respect to drying conditions. Further, there were descriptions regarding an achievement of enhanced external quantum efficiency of a device, which were related to polymeric materials, not including any low-molecular-weight material, and in which there was no consideration with respect to drying conditions (such as described in, for example, Patent document 3).